1. Field of the Invention
The present invention relates to a communication method of data.
2. Description of the Related Art
In recent years, transmission and reception of moving image data via a network have sharply increased. A real-time transport protocol (RTP) is generally used as a technology for stream transmission of the moving image data in real time through a network such as the Internet or a local area network (LAN).
Further, transmission and reception of information relating to the moving image stream transfer are performed in parallel with a stream transfer through the RTP, between a transmission apparatus and a reception apparatus, which respectively transmits and receives the moving image stream using the RTP. A real-time transport control protocol (RTCP) is often used for the transmission and reception of the information relating to the moving image stream transfer.
RTCP data, which the reception apparatus transmits to the transmission apparatus, includes reception status information (receiver report), a retransmission request for a packet which the reception apparatus has failed to receive, and the like. On the other hand, RTCP data, which the transmission apparatus transmits to the reception apparatus, includes a sender report and the like.
The reception status information includes, for example, a missing ratio of the received packets by the reception apparatus and a packet interval jitter. The transmission apparatus can adjust transmission rates of the moving image data, and rates of forward error correction (FEC) data, based on the reception status information received from the reception apparatus.
Japanese Patent Application Laid-Open No. 2001-320440 discusses, based on data loss ratio information from a transmission destination of data, controlling transmission rates of the data by the transmission apparatus since then. However, there is a possibility that appropriate communication control cannot be performed, depending on a transmission timing of the reception status information by the reception apparatus.
For example, if a transmission interval of the reception status information by the reception apparatus is long, the reception apparatus cannot respond quickly to a change of the communication status of the network. That is, even when congestion occurs on the network, there is a possibility that a start of processing for lowering the transmission rate will be delayed due to its delayed detection.
On the other hand, if the transmission interval of the reception status information by the reception apparatus is short, there is a possibility that a load imposed on transmission and reception of the reception status information and a traffic of the network will become larger more than necessary.